Oral 5, Expanding choice for prenatal testing in couples at reproductive risk of Herlitz junctional epidermolysis bullosa

Abstract

Following the early demise of their first child with Herlitz junctional epidermolysis bullosa (HJEB) a couple wished to consider prenatal testing. An immediate option would be fetal skin biopsy (FSB), a technique available for over 25 years, based on transmission electron microscopy and immunohistochemical analysis of laminin-332 expression, looking for similar changes to those in the deceased child's skin. However, this test could only be conducted after 15 weeks’ gestation and was not acceptable to this family. Mutation analysis was therefore performed on the laminin-332 genes by heteroduplex analysis and direct nucleotide sequencing and the deceased child was shown to be a compound heterozygote for the LAMB3 nonsense mutation p.R635X (maternal) and splice site mutation c.3228G→A (paternal). With this information, chorionic villus sampling (CVS) with DNA sequencing could be conducted at an earlier gestation (10–11 weeks). However, both FSB and CVS involve termination of an affected pregnancy. An alternative option is preimplantation genetic diagnosis (PGD), based on DNA analysis of single blastomeres extracted from late cleavage stage embryos following in vitro fertilization. We have therefore developed a novel generic PGD test for HJEB based on whole genome amplification of DNA from single blastomeres, followed by multiplex polymerase chain reactions analysing 12 linkage markers within and flanking the LAMB3 gene. This assay is now licensed for clinical use in the U.K. and its suitability for this couple is being assessed. The development of PGD broadens personal choice for couples at reproductive risk of HJEB and represents a useful translational advance from basic research into epidermolysis bullosa.